Authenticity in Fiction

I love reading a good book and appreciate how wonderfully researched so many of our favorite authors are. When the setting of the book is in the 1800's and is not true to the era, it feels a bit out of sync. In a recent book I read the heroine comments on how unfair it is that men seemed to be allowed much more freedom in society than women. She reflected on the "gender" differences and what she would do if the could change things. Jane Austen, who more than once reflected on this topic, would have talked about the difficulties of her sex, meaning, of course, being a woman.
Another instance came from a book that was highly recommended to me. The heroine is frustrated when a young man she disagrees with tells her how he handles things...."How's that working out for you?"  From then on I decided there are too many well written books that I can spend my time reading.

I am not a writer, have never published any works but when I read them, I want a well written book to read. I am at risk right now of slighting the punctuation experts but I want to visualize the setting, meet the characters and enjoy the author's story.  I don't want to read slang that is not relative to the setting of the book.